Vitamin K

What is vitamin K used for?

Updated 3 Nov 2026

Short answer

The best-proven use is one injection of vitamin K for newborn babies: it prevents bleeding in the first week of life.[1] In adults, most trials studied bones and the heart and arteries, and the results are mixed:[2][3]

  • Bones. A 2019 review of 36 trials found no evidence of an effect on bone density or spine fractures in women after menopause or people with osteoporosis. The odds of any clinical fracture were 28% lower, but the review judged the evidence not enough to confirm this.[2]
  • Arteries. In 9 trials, vitamin K did not consistently slow calcium build-up or stiffening of the arteries.[3] A 2026 trial of 360 µg of MK-7 a day found slower calcium build-up in people with coronary artery disease.[4]
  • Leg cramps. One trial in 199 adults aged 65 and older found fewer night-time leg cramps with 180 µg of MK-7 a day.[5]
  • Blood sugar. Two meta-analyses found a small drop in insulin resistance. Only one of them also found lower fasting blood sugar.[6][7]

Sources (7)

  1. Prophylactic vitamin K for vitamin K deficiency bleeding in neonates. Puckett RM, Offringa M Cochrane Database Syst Rev, 2000. PMID 11034761
  2. Effect of vitamin K on bone mineral density and fractures in adults: an updated systematic review and meta-analysis of randomised controlled trials. Mott A, Bradley T, Wright K, Cockayne ES, Shearer MJ, Adamson J, et al. Osteoporos Int, 2019. PMID 31076817
  3. Vitamin K Supplementation for the Prevention of Cardiovascular Disease: Where Is the Evidence? A Systematic Review of Controlled Trials. Vlasschaert C, Goss CJ, Pilkey NG, McKeown S, Holden RM Nutrients, 2020. PMID 32977548
  4. Two Years of Menaquinone-7 Supplementation and Coronary Artery Calcification: A Randomized Clinical Trial. Vossen LM, de Leeuw PW, Schurgers LJ, Heuts S, Adriaans BP, de Haan C, et al. JAMA Cardiol, 2026. PMID 42268593
  5. Vitamin K2 in Managing Nocturnal Leg Cramps: A Randomized Clinical Trial. Tan J, Zhu R, Li Y, Wang L, Liao S, Cheng L, et al. JAMA Intern Med, 2024. PMID 39466236
  6. The relationship between vitamin K and T2DM: a systematic review and meta-analysis. Qu B, Yan S, Ao Y, Chen X, Zheng X, Cui W Food Funct, 2023. PMID 37724446
  7. The effect of vitamin K supplementation on cardiovascular risk factors: a systematic review and meta-analysis. Zhao QY, Li Q, Hasan Rashedi M, Sohouli M, Rohani P, Velu P J Nutr Sci, 2024. PMID 38282652

More about vitamin k

What is vitamin K?Which foods contain vitamin K?Who is at risk of vitamin K deficiency?Is vitamin K safe?Why do newborn babies get vitamin K?Does vitamin K help keep bones strong?

For education; not medical advice. Talk to a doctor before you start, stop or change a supplement.